Anthocyanin pigments will appear as red and carotenoids can be seen as orange, yellow or red. Together they make more orange. Less of one or the other more yellow. The absence of these pigments show up as brown in some oak tree leaves.
I love leaves, I love trees, walking in the woods or anywhere there are trees reminds me how small I am in this natural world. As a kid we played hide'n'seek using trees as our home base. I climbed trees, started to study their bark, form, leaf patterns and of course picked up fallen leaves. To this date I still collect leaves and still think of trees as my home base.
Not to stray to far from the paper making going on this week. I embed leaves into the hand made paper, I let them create an embossing in wet paper as the paper dries or the small leaves float in the pulp water and find their way into the paper. To do this you must let the leaf dry or those pigments will bleed into the wet pulp.
There are many ways to preserve or dry leaves. I use the very old method of putting them in a phone book. Those big old yellow colored ones and just leave them for a while. You can iron them in-between wax paper but then I don't think I would like that in the hand made paper. You can microwave them, which I have not tried or soak them in glycerin & water. I think I will still with the phone books for now.
In the Northern Hemisphere the first day of fall is September 22, 2013 this Sunday. Take some time, take a walk, see what changes in the leaves are happening in your area. Take pictures, collect a couple leaves, listen to nature talking to you and breath, the air always smells different in the fall.